Updated

Negotiators from the United States and eight other Pacific Rim countries opened a round of talks Monday aimed at producing one of the most ambitious trade deals in decades amid criticism that the deliberations are shrouded in secrecy.

The United States has been negotiating the Trans-Pacific Partnership Free Trade Agreement for about three years. The talks include Australia, Brunei, Chile, Malaysia, New Zealand, Peru, Singapore and Vietnam. Mexico and Canada are expected to join, and Japan has expressed interest.

Last week, two-thirds of House Democrats wrote to U.S. Trade Representative Ron Kirk — the White House's top trade official — complaining they were being left out of the loop on the pact.

Rep. Darrell Issa, Republican chairman of the House Oversight and Government Reform Committee, sought unsuccessfully to observe the 13th round of talks, which run through July 10. Issa said the talks should not be "a secretive backroom negotiation."

About 100 protestors peacefully demonstrated outside the downtown hotel where the talks opened. Critics said the talks threatened climate change laws, regulation of financial markets, labor rights and environmental and health protections.

"Let us say, 'open these negotiations to the people,'" U.S. Rep. Bob Filner, a San Diego Democrat, told the crowd. "Let's stop this so-called free trade."

U.S. officials insist they have been as open as they have ever been on a trade agreement. They say making public their negotiating positions would undercut their leverage in the talks with other countries.

President Barack Obama said in November he was optimistic an agreement would be reached this year, before Mexico and Canada were slated to join.

Hundreds of critics and supporters who registered two weeks in advance had a chance to speak directly with negotiators in an exhibit hall. About 50 groups set up tables with signs that revealed sharply different and sometimes competing agendas. Among them were the Green Party, Rubber and Plastic Footwear Manufacturing Association, Democratic Socialists of America, San Diego Regional Chamber of Commerce and Teamsters union.

Jodie Griffin, an attorney for the Public Knowledge advocacy group, told a U.S. negotiator that she worried that copyright protections in the pact would be too severe and harmful to consumers. She also said negotiating documents should be open to public view.

"We're trying to be as transparent as possible," responded Michael Masserman, executive director of export policy at the U.S. Commerce Department. "Lots of sensitivities in the (intellectual property) negotiations."

The public forums are an opening day staple, at least for rounds held in the United States. Negotiators slowly walked the aisles, politely engaging skeptics seated at tables. Several additional rooms were set up for speakers to give 10-minute presentations to larger audiences.

Some negotiators "are lapdogs for the big corporations," Ernest Verano, 49, an employee of a San Diego pharmaceutical company whose table displayed a handwritten sign criticizing the North American Free Trade Agreement, told a Malaysian delegate.

The delegate, who declined to give her name, listened politely to his concerns and said the group will try to do its best.

The San Diego round is not expected to produce a final agreement. The U.S. delegation is led by Barbar Weisel, assistant U.S. trade representative for Southeast Asia and the Pacific.